Oil burner system with motor-driven pump controlling bypass valve

ABSTRACT

An oil burner system in which a fuel oil pump and the air blower are independently driven by a common motor having a single stator and two independently driven rotors. One rotor is connected to the pump and the other to the air blower so that the inertia of the pump drive is reduced and it comes to a stop quicker. The rotor for driving the pump is disposed in an oil-filled compartment so that it is damped. The system is provided with a bypass valve connecting the discharge side of the pump with its suction controlled by the motor shaft which is biased to open the bypass valve when the motor is in a deenergized condition. When the motor is energized the shaft is attracted axially electromagnetically and it closes the bypass valve. When the motor is deenergized it opens the bypass valve, the pump stops relatively quickly and the blower continues to blow air to ensure burning of all oil supplied from the burner and avoid coking on the burner and elsewhere.

ilnited Mates Patent 72] Inventor Kyrre Guttorm Sjotun Nordborg, Denmark [21] Appl. No. 727,836 [22] Filed May 9, 1968 [45] Patented Nov. 2, 1971 [73] Assignee Danfoss AllS Nordborg, Denmark [32] Priority May 9, 1967 [33] Germany [31] D 53036 [54] OH. BURNER SYSTEM WITH MOTOR-DRIVEN PUMP CONTROLLING BYPASS VALVE 1 Claim, 3 Drawing Figs.

[52] 11.8. CI 417/299, 239/127 [51] lint. Cl .F04b 13/09, BOSb 9/00 [50] Field ofSearch .239/125-127; 103/6, 7, 87, 221, 42,112, 87; 417/299 [56] Reierences Cited UNITED STATES PATENTS 1,799,902 4/1931 Hoff 103/221 X 5 I2 j? l9 Primary Examiner Robert M. Walker A ttarney- Wayne B. Easton ABSTRACT: An oil burner system in which a fuel oil pump and the air blower are independently driven by a common motor having a single stator and two independently driven rotors. One rotor is connected to the pump and the other to the air blower so that the inertia of the pump drive is reduced and it comes to a stop quicker. The rotor for driving the pump is disposed in an oil-filled compartment so that it is damped. The system is provided with a bypass valve connecting the discharge side of the pump with its suction controlled by the motor shaft which is biased to open the bypass valve when the motor is in a deenergized condition. When the motor is energized the shaft is attracted axially electromagnetically and it closes the bypass valve. When the motor is deenergized it opens the bypass valve, the pump stops relatively quickly and the blowercontinues to blow air to ensure burning of all oil supplied from the burner and avoid coking on the burner and elsewhere.

wt 2 1m 15 I0 7 r. r

OIL BURNER SYSTEM WITH-ll MOTOR-DRIVEN PUMP CONTROLLING BYPASS VALVE This invention relates generally to oil burners and more par ticularly to an oil burner system comprising an motor-driven pump which controls a burner nozzle bypass valve.

The usual oil burner system has a motor which drives both the fuel oil pump and the air supply source, for example, a blower. When the motor is turned off it continues to rotate due to the inertia of the assembly connected thereto. Thus fuel oil continues to be fed by the fuel oil pump at a diminishing pressure for a relatively long period of time. This oil tends to drip fromthe nozzle as the pressure is reduced and the nozzle and areas on which the oil impinges become coked. It has been the common practice to insert complicated cutoff valves between the pump and the nozzle for precluding this kind of drippage. The cutoff valves responded to the oil pressure, for example, and effect closure rapidly as soon as the oil pressure drops below a predetermined level.

It is also known to bypass the burner nozzle by means of a bypass valve which is electromagnetically controlled to open when the pump is switched off and its driving motor is deenergized. In that kind of system the bypass valve may be in an open condition when the pump is started and begins to take a suction. Such electromagnetically actuated bypass valves are electrically connected to the pump motor circuit.

It is a principal object of the present invention to provide an oil burner system in which the problem of dripping oil, when the oil pump motor is turned off, is eliminated.

Another object of the present invention is to provide an oil burner system in which the avoidance of dripping oil once the pump is turned off is effected by simple means including an improved bypass valve and dispenses with the additional circuitry generally required for activating the valve electromagnetically in conjunction with the pump motor circuit.

ln the oil burner system according to the invention an oil burner is supplied fuel oil by a fuel oil pump and a blower provides air for combustion of the oil. A single, common motor drives the oil pump and the air blower independently of each other. The motor comprises a single stator and has a rotor which is divided into coaxial parts one of which drives the pump and the other the blower independently of each other.

The oil pump motor shaft actuates a valve element opening and closing a bypass valve, in a bypass line, allowing oil to pass from the discharge or pressure side of the pump to the suction side when the pump motor is deenergized and closing the valve when energized. Oil delivered by the pump after the pump motor is switched off flows directly through the bypass line to the suction side of the pump immediately after the switching off takes place so that oil does not reach the burner nozzle. if the bypass line does not accept all the oil from the pump the pressure in the pressure line between the pump and burner nozzle drops rapidly and it is possible to control complete cutoff of delivery to the nozzle with a cutoff valve of simple design. In any case because of the rapid cutting off of supply of oil to the nozzle the blower can be constructed to have higher speed than known constructions even if coupled to the motor in the conventional way rather than being decoupled therefrom as in the embodiment of the invention herein described. Furthermore, in contrast to the known cutoff valves the arrangement according to the invention is independent of the size of the nozzle.

A feature of the construction is that the inertia of the rotating parts associated with the pump is considerably reduced. Thus when the motor is turned off it comes to a stop more rapidly than heretofore in motors in which the pump and air supply source are mounted to be jointly driven from a com mon rotor. Thus when the motor is turned off less fuel oil is supplied and this avoids the dripping of oil that takes place if the pump does not stop rapidly. Moreover, the air blower is not braked or clamped by the pump so that it runs freely for a considerably longer time and therefore provides continuously a flow of air so that oil that would tend to drip is consumed and blown away from the nozzle so that coking is not possible.

The use of independent drive for the oil pump and blower and the bypass valve of the invention means that upon switching off the apparatus the oil burner system need not have a cutoff valve or if it is desired to use one it can be of a simple design.

A fluidtight partition is disposed between the two rotors within the stator and motor housing and defines a compartment in which the rotor driving the pump is disposed. Oil from the pump is delivered into this compartment during operation so that the rotor driving the pump is damped or braked so that the pump comes to a stop relatively quickly after the motor has been switched ofi. This type of construction avoids the need of a stuffing box between the pump and the oil-filled compartment of the motor so that the pump shaft rotates with considerably less friction. The reduced friction increases performance characteristics which readily make up for the losses caused by the damping oil in the oil-filled compartment. Moreover, the oil in this compartment effects cooling of the stator and the rotor within the compartment and is effective in reducing noise during operation.

In order to particularly maintain the motor cooled in extensive operation the oil-filled compartment in the motor is delivered from the pressure side of the pump through a pressure-regulating valve and/or cutoff valve. As soon as the motor has been turned on and reaches speed the oil under pressure is circulated through the oil-filled compartment so that a good cooling effect is achieved during operation. The cutoff valve employed in conjunction with the invention comprises a spring-loaded pressure regulator valve of known type having an extension which directly closes the nozzle or burner supply line. Other known pressure-regulating valves can perform the cutoff function. In any event even if the arrangement is such that oil is not circulated during operation the bypass valve of the invention allows oil to circulate to the oil-filled compartment of the motor rotor each time the motor is switched off since the bypass line, in which the bypass valve is disposed, connects the pressure side of the pump to the suction side thereof through the motor oil-filled compartment.

The motor and pump construction is such that the motor shaft connected to one of the rotors constitutes the pump shaft. The pump shaft actuates the valve element of the bypass valve of the system according to the invention. The invention takes advantage of the normal tendency ofa rotor to move axially of the stator when a motor is deenergized. The pump shaft is positively biased or mechanically forced in an axial direction for rapidly opening the bypass valve. in the particular embodiment described the pump shaft defines the bypass valve element which opens the valve by being moved axially positively by a spring and is attracted electromagnetically in an opposite axial direction closing the valve when the pump motor is energized.

Other features and advantages of the oil burner system in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawings in which:

FIG. 1, is an elevation sectional view of a motor drive and oil pump for the oil burner system in accordance with the invention;

FIG. 2, is a diagram of an oil burner system according to the invention; and

FIG. 3, is a fragmentary section view of a pressure-regulating and cutoff valve used in an oil burner system in accordance with the invention.

As illustrated in the drawing a motor drive for an oil burner system as hereinafter constructed is shown in FIG. 1 and comprises a stator 1 with a inding 2 held in two half-shells 3, 4 of a motor housing. Within the stator is mounted for rotation a first rotor or rotor part 5 driving a shaft 6 which rotationally drives an air blower 7. A second rotor or rotor part 8 independent of the other rotor is mounted coaxially with the other rotor and rotatably drives a shaft, 9 connected to a pump l0. The shaft 6 is mounted coaxial with a bearing bushing ll and extend through an end wall of the half-shell 3 of the housing.

The shaft 6 is secured against axial displacement by means ofa locking device 12. The pump shaft 9 is mounted in two bearing bushings 13, 14 coaxially disposed in a pump housing 15 which is secured in a central opening in the housing half-shell 4 by a ring 16 and circumferentially disposed screws 17.

The two rotor parts 5, 8 are separated from each other by a fluidtight partition 18. The partition is part of a cup-shaped member 19 having the walls of the cup part of the member bear against the stator l and the inner surfaces about the mouth of the cup-shaped member bear against the circumference of an annular part 21 of the housing. This housing part has an annular recess in which is disposed a seal ring 20 effecting a seal between the inner surfaces of the mouth of the cupshaped member and the portion 21 of the housing. In this manner an oil chamber or compartment 22 is defined by the parts 3, 4, 15, 16, and 19. This compartment or chamber is part of an oil circulation path and is oil filled during operation as illustrated in FIG. 2 and hereinafter explained.

The overall burner nozzle system is illustrated diagrammatically in FIG. 2. The pump is connected to a suction line 23 which takes a suction from an oil sump 24 and delivers it to a pressure discharge line or passage 25 to a valve arrangement 26 which comprises a pressure-regulating valve and a cutoff valve hereinafter described. When the cutoff valve is open, oil under pressure flows to a nozzle 27 which delivers oil to be burned into a combustion chamber of the burner, not shown. The excess oil which is not required flows through a return passage 28 in communication with the chamber 22 and back through an outlet to the sump 24 or to the suction side of the pump as illustrated. Those skilled in the art will understand that the pump 10, the valve unit 26 and the associated lines or passages may be constructed as one unit. The pump housing can, for example, house the valve system 26 and the passages, for example the passages 25 and 28.

A bypass line 29 having a bypass valve 50 connected therein connects the pressure or discharge line 25 with the oil-filled compartment or chamber 22 and therefore with the suction side of the pump as illustrated in FIG. 2. The shaft 9 of the motor can move axially outwardly as indicated by the arrow designated P. The valve 50 is actuated by the shaft 9 through a mechanical connection therewith, for example, a rod, illustrated diagrammatically by a broken line so that pump shaft controls opening and closing ofthe valve as later described. In an embodiment of the invention the pump 10, cutoff valve 26, the bypass valve 50 and the associated oil lines can be constructed as a structural unit. The pump housing 15, for example, can contain the valve arrangement 26, 50 and the lines 25, 28, 29 may be made as passages in the housing.

In the construction illustrated in FIG. 1 the shaft 9 is axially displaceable in the bushing bearing 13, 14. It is biased to the right, in the direction of the arrow P, by means of a spring 30 applying force axially of the shaft. When the motor is deenergized the spring moves the shaft 9 outwardly opening the bypass valve. When the motor is energized the shaft 9 is drawn toward the opposite direction, toward the left in the drawing, by the magnetic forces developed by the motor.

In one embodiment of the present invention the pump shaft and housing define the valve without need of connection thereto. In such an embodiment of the bypass valve illustrated in FIG. I an enlarged cylindrical portion 31 of the shaft 9 defines a valve element and closes a passage 32 leading from the pressure side 33 of the oil pump to a connecting passageway 34 communicating with the chamber or compartment 22. The shaft is assumed to be in its attracted position closing the bypass valve. Displacement of the shaft 9 is, of course, relative to the inner gear wheel of the gear pump 10. As soon as the motor is switched off the spring 30 displaces the shaft toward the right toward the pump in the axial space provided for axial movement and the passageway 32 is thus opened. Oil under pressure will then flow directly through the passageways 32, 34 and the oil chamber 22 to the suction side of the pump.

A pressure-regulating and cutoff valve 36, FIG. 3, may be mounted in the pump housing 15 for carrying out pressure regulation and cutoff of fuel oil supply to the nozzle 27 when the fuel oil pump is stopped. This valve carries out the functions of the valve 26 shown in FIG. 2. A bore 37 is provided in the housing 15 and at one end thereof a threaded plug 38 which comprises a nozzle supply outlet 39 and a valve seat 40 for the cutoff valve. At the other end of the valve bore is provided a threaded bushing hollow cap 41 having a closed end and movable axially to adjust a spring 42 housed internally thereof. The spring biases valve element 43 of a pressure-regulating valve, which is axially guided in a bushing 44 acting in the manner of a guide slide, toward a seated position. The valve element 43 has an axial extension 45 which forms the cutoff valve.

A passageway 46 is in communication with the pressure line or passage 25 and another passage 47 corresponds to the return line or passage 28. Thus when a certain pressure is applied through the inlet passage 46 the valve unseats against the action of the spring 42 and at a reduced pressure, after the pump is switched off, the cutoff valve extension 45 will seat on the valve seat 40 cutting off supply of fuel oil to the nozzle. During the time that the valve, however, is seated cooling oil flow is permitted through the compartment 22 through passageway 47 as heretofore described.

Those skilled in the art will understand that the principles of the invention are equally applicable to constructions in which the motor only drives the pump and to constructions in which the blower and the pump are mounted on a common shaft. The construction illustrated wherein the pump and blower are separated and driven by a single motor provides a single, inexpensive construction and the separation of the blower from the pump reduces inertia so the pump will stop more quickly when the motor is turned off. Moreover, the pump motor may have a vertically disposed shaft in which case gravity can be taken advantage of actuating the shaft axially for controlling a bypass valve. A spring acting in conjunction with a spring can rapidly open a bypass valve and the axial attraction of the rotor can close such a bypass valve. This can be accomplished, for example, by using a known motor with a tapered airgap.

While preferred embodiments of the invention have been shown and described it will be understood that many modifications and changes can be made within the true spirit and scope of the invention.

What I claim and desire to be secured by Letters Patent is:

1. In combination, a fuel oil supply pump, a fuel oil cooled electric motor having a winding electrically energized in operation, a shaft on said pump driven from said motor, means mounting said shaft for rotation and movement axially, means defining a bypass flow path bypassing fuel oil from a discharge side of said pump to a suction side thereof for cooling said motor, said means defining said bypass flow path comprising a bypass valve, said shaft comprising a valve element of said bypass valve operable axially and effective to bypass fuel oil when said motor winding is deenergized and to close said bypass valve when said motor is energized, biasing means biasing said shaft axially in a direction for opening said bypass valve, and said winding being disposed relative to said shaft attracting said shaft electromagnetically in a direction axially against force applied by said biasing means thereby to close said bypass valve, whereby fuel oil flows under pressure through said flow path when said motor is deenergized and said motor and pump continue to rotate under the control of the inertia thereof. 

1. In combination, a fuel oil supply pump, a fuel oil cooled electric motor having a winding electrically energized in operation, a shaft on said pump driven from said motor, means mounting said shaft for rotation and movement axially, means defining a bypass flow path bypassing fuel oil from a discharge side of said pump to a suction side thereof for cooling said motor, said means defining said bypass flow path comprising a bypass valve, said shaft comprising a valve element of said bypass valve operable axially and effective to bypass fuel oil when said motor winding is deenergized and to close said bypass valve when said motor is energized, biasing means biasing said shaft axially in a direction for opening said bypass valve, and said winding being disposed relative to said shaft attracting said shaft electromagnetically in a direction axially against force applied by said biasing means thereby to close said bypass valve, whereby fuel oil flows under pressure through said flow path when said motor is deenergized and said motor and pump continue to rotate under the control of the inertia thereof. 